Protein biomarker may aid earlier breast cancer detection

Levels of a protein implicated in several cancers—epidermal growth factor receptor—may be elevated in the blood of women up to 17 months prior to their breast cancer diagnosis, according to findings presented last month at the American Association for Cancer Research annual meeting.

The goal of the study, led by Dr. Chris Li in the Public Health Sciences Division’s Epidemiology Program, was to discover and validate blood markers that could potentially be used for the early detection of breast cancer.

The study was conducted on 420 patients with estrogen receptor-positive breast cancer whose blood was drawn up to 17 months before their diagnosis. The researchers validated promising markers in a similar, independent set of nearly 200 cases and controls from the Women's Health Initiative database.

Li found EGFR levels were significantly elevated among the breast cancer cases. Overall, those with the highest levels were almost three times more likely to develop breast cancer compared to those with the lowest level.

Among women using estrogen plus progestin hormone therapy, those with the highest EGFR levels were nine times more likely to develop breast cancer compared to the women with the lowest levels. As a single marker among the hormone users, EGFR levels correctly identified 90 percent of women who did not develop breast cancer, but only 31 percent of women who developed breast cancer.

Li said EGFR alone did not prove useful as a biomarker for breast cancer detection, but it would likely be valuable in a panel of such markers.

“This study is unique in that no prior studies have validated a single early detection biomarker for breast cancer to the degree we have here,” Li said. “Our results suggest that there may indeed be detectable changes of proteins in blood within two years of making a clinical breast cancer diagnosis. Identification of these proteins could have a major impact on our ability to detect breast cancer early, when it is most treatable.”

EGFR is part of the HER2 family, which has been shown to be significant in breast cancer. EGFR is elevated in 20 percent to 81 percent of all human breast cancers. Several therapies targeting members of the HER2 family, including EGFR, have already been approved for cancer treatment.

[Adapted from an AACR news release]